Discharge of pumpable material from plastic or flexible bags lining intermediate bulk material shipping containers.
As related in the background section of U.S. Pat. No. 6,234,351, many problems have interfered with full evacuation of pumpable or flowable bulk material contents from plastic bags lining intermediate bulk material shipping containers. These containers can be handled by forklifts and arranged conveniently in trucks, railroad cars, ships, or planes where each container holds typically around 300 gallons of flowable or pumpable bulk material contained within a plastic liner bag.
For several reasons the shipping container industry prefers that bottoms for such containers be flat. It also prefers to avoid the problems of tilting containers for discharge of their contents, elevating containers for this purpose, or requiring manual intervention to be sure that most of the shipped material is successfully discharged from each container. The full discharge of shipped material becomes especially problematic with highly viscous materials such as mayonnaise or dry wall paste, and with powdered or granular materials that are barely flowable or pumpable.
The aim of the inventions of U.S. Pat. No. 6,234,351, parent application Ser. No. 09/765,176 and this application, is to solve the problems of full content evacuation from bag-lined liquid shippers in an inexpensive, effective, and labor free way. To this purpose, the subject matter of this application adds to and refines similar subject matter previously disclosed in U.S. Pat. No. 6,234,351 and parent application Ser. No. 09/765,176.
The present system of enhancing discharge of pumpable material from a liner bag of a liquid shipper uses a bag having an inflatable region formed of a pair of plies secured together to enclose an air containment region. This is preferably done without using any material additional to what is already committed to the structure of the bag itself. The securing of the bag plies is configured so that when the bag is disposed within a supporting container, the air containment region is disposed outside a material discharge zone arranged at the bottom of the bag. The inflatable air containment region may also extend above the bottom of the bag, providing this does not interfere with discharge of material from the bag.
As material discharges from the bag, a delivery system urges air into the air containment region. As the weight of material remaining in the bag permits, the air inflates the air containment region outside the discharge zone, and this inflates or plumps the air containment region outside the discharge zone. Plumping the bag effectively raises above the bottom of the container a ply of the bag contacting the material to form the bag into a sump shape at the discharge zone. Gravity then makes the material flow downward along the slope of the raised ply toward the sump in the discharge zone where the material is discharged from the bag. The discharge can occur via a gravity drain, a pumped drain, or a pumped discharge up through a top of the bag and above the top of the container.